John J. Mates, 92, a member of the United Mine Workers of America International Board for almost 50 years and the longtime executive assistant to former UMWA leader John L. Lewis, died May 4 in Pottsville, Pa.

Born in Cletormoor, England, Mr. Mates came to this country with his family at the age of one. He began to work in the mines as a breaker boy when he was 9 after his father broke his back in a mining accident and the youngster had to help support the family.

Mr. Mates, who held elective office in the UMWA longer than anyone else in the union's history, was imbued with unionism at an early age and at a time in American history when unions were struggling to organize against sometimes overwhelming odds.

Mr. Mates was working in the Williamstown Colliery breaker in 1900 when John Mitchell began an organizational campaign that Mates joined and that cost him his job. Mr. Mates returned to work as a mule driver after a six-week strike and continued his union activism.

He served as president and member of the Mine Committee of Local Union 1550 before his election in 1918 to the International Board, to which he would be re-elected for a period covering 47 years until his retirement in 1966.

Mr. Mates served on international commissions in the United States and Canada and in 1948 represented the UMWA at the sessions of the International Confederation of Free Trade Unions held in Paris.

The former miner played a role in the formation of the Congress of Industrial Organizations (CIO) and once told an interviewer that he believed the formation of the CIO and its organizing of millions of workers was one of the outstanding contributions of the UMWA to humanity.

During his long association with the union Mr. Mates served also as Regional Director of the steelworkers' union in Baltimore and during the Kennedy administration served on the President's Committee on Employment of the Handicapped.

Surviving are two daughters, Ruth F. Mates of Williamstown, Pa. and Mrs. Marion E. Walter, of Washington; and two granddaughters.